linux系统通信功率信道修改方法

2024-05-29 12:43| 来源: 网络整理| 查看: 265

linux系统通信功率信道修改方法配置频段可以先查看有哪些频段：

iwlist channel

可用信道123456789101112131415wlan0 13 channels in total; available frequencies : Channel 01 : 2.412 GHz Channel 02 : 2.417 GHz Channel 03 : 2.422 GHz Channel 04 : 2.427 GHz Channel 05 : 2.432 GHz Channel 06 : 2.437 GHz Channel 07 : 2.442 GHz Channel 08 : 2.447 GHz Channel 09 : 2.452 GHz Channel 10 : 2.457 GHz Channel 11 : 2.462 GHz Channel 12 : 2.467 GHz Channel 13 : 2.472 GHz Current Frequency:2.422 GHz (Channel 3)

改变信道

sudo iwconfig wlan1 channel 1

iwlist channel显示：

1213 channels in total; available frequencies : Current Frequency:2.412 GHz (Channel 1) 修改发射功率

sudo iwconfig wlan1 txpower X

Tx 是发射（Transmits）的简称。无线电波的发射功率是指在给定频段范围内的能量，通常有两种衡量或测量标准：

功率（W）：相对1 瓦（Watts）的线性水准。例如,WiFi 无线网卡的发射功率通常为0.036W ，或者说36mW。增益（dBm）：相对1 毫瓦（milliwatt）的比例水准。例如,WiFi 无线网卡的发射增益为15.56dBm。功率单位mW 和dBm 的换算： dBm = 10 * lg[ 功率mW] //即，以10为底数取[功率mW]对数，然再乘以10 mW = 10^[增益dBm / 10dBm] //即，以10为底数，[增益dBm/10dBm]为指数，计算取值 1234567891011121314151617 10 W 的无线发射功率为 40 dBm 6.4 W 的无线发射功率为 38 dBm 3.2 W 的无线发射功率为 35 dBm 1.6 W 的无线发射功率为 32 dBm 1000 mW 的无线发射功率为 30 dBm 800 mW 的无线发射功率为 29 dBm 400 mW 的无线发射功率为 26 dBm 200 mW 的无线发射功率为 23 dBm 100 mW 的无线发射功率为 20 dBm 50 mW 的无线发射功率为 17 dBm 25 mW 的无线发射功率为 14 dBm 12.5 mW 的无线发射功率为 11 dBm 10.34 mW 的无线发射功率为 10 dBm 8.26 mW 的无线发射功率为 9 dBm 6.25 mW 的无线发射功率为 8 dBm 3.125 mW 的无线发射功率为 5 dBm 1 mW 的无线发射功率为 0 dBm

经测试树莓派的发射功率最大可以达到31dBm、linux电脑可以达到20dBm。树莓派可以通过命令行切换信道，linux电脑无法切换信道。和学长讨论后不知道是不是伪切换信道需要进行测试。

测试是否为伪切换

让树莓派连接到一个固定信道的路由器进行测试。

若无法切换信道则可以推断，树莓派确实能够切换上行信道

若可以切换信道，且可以上传则证明树莓派伪切换信道

实验准备一个路由器，将信道调整为固定信道1，树莓派尝试进行连接(修改配置文件)。测试是否连接到固定信道路由器123456789iwconfigwlan0 IEEE 802.11bgn ESSID:"CH1" Mode:Managed Frequency:2.412 GHz Access Point: C8:3A:35:58:A4:D8 Bit Rate=72.2 Mb/s Tx-Power=31 dBm Retry short limit:7 RTS thr:off Fragment thr:off Power Management:on Link Quality=70/70 Signal level=-38 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:5 Invalid misc:0 Missed beacon:0 12345678ping 192.168.2.100PING 192.168.2.100 (192.168.2.100) 56(84) bytes of data.64 bytes from 192.168.2.100: icmp_seq=1 ttl=64 time=641 ms64 bytes from 192.168.2.100: icmp_seq=2 ttl=64 time=143 ms64 bytes from 192.168.2.100: icmp_seq=3 ttl=64 time=64.2 ms64 bytes from 192.168.2.100: icmp_seq=4 ttl=64 time=84.8 ms64 bytes from 192.168.2.100: icmp_seq=5 ttl=64 time=214 ms64 bytes from 192.168.2.100: icmp_seq=6 ttl=64 time=141 ms

结论:以上测试证明树莓派有正确连接到路由器

测试树莓派是否能切换信道 iwlist channel显示：12345678910111213wlan0 11 channels in total; available frequencies : Channel 01 : 2.412 GHz Channel 02 : 2.417 GHz Channel 03 : 2.422 GHz Channel 04 : 2.427 GHz Channel 05 : 2.432 GHz Channel 06 : 2.437 GHz Channel 07 : 2.442 GHz Channel 08 : 2.447 GHz Channel 09 : 2.452 GHz Channel 10 : 2.457 GHz Channel 11 : 2.462 GHz Current Frequency:2.412 GHz (Channel 1)

2.切换信道

sudo iwconfig wlan0 channel 3

123456iwconfigwlan0 IEEE 802.11bgn ESSID:"CH1" Mode:Managed Frequency:2.422 GHz Access Point: Not-Associated Tx-Power=31 dBm Retry short limit:7 RTS thr:off Fragment thr:off Power Management:on

信道被修改了

尝试进行ping12345678ping 192.168.2.109PING 192.168.2.109 (192.168.2.109) 56(84) bytes of data.64 bytes from 192.168.2.109: icmp_seq=1 ttl=128 time=9.72 ms64 bytes from 192.168.2.109: icmp_seq=2 ttl=128 time=6.33 ms64 bytes from 192.168.2.109: icmp_seq=3 ttl=128 time=22.0 ms64 bytes from 192.168.2.109: icmp_seq=4 ttl=128 time=44.1 ms64 bytes from 192.168.2.109: icmp_seq=5 ttl=128 time=8.24 ms64 bytes from 192.168.2.109: icmp_seq=6 ttl=128 time=7.62 ms

传输正常…

结论:树莓派很有可能是伪切换上行信道，但是我没有办法排除固定信道路由器无法接受非该信道信号的这个可能性。

进一步实验

如果修改信道可能xmu201_1的信道会改变。

123456789101112131415161718192021222324252627282930313233343536iwlist scanCell 05 - Address: D4:EE:07:49:19:FC Channel:3 Frequency:2.422 GHz (Channel 3) Quality=70/70 Signal level=-39 dBm Encryption key:on ESSID:"xmu201_1" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 9 Mb/s 18 Mb/s; 36 Mb/s; 54 Mb/s Bit Rates:6 Mb/s; 12 Mb/s; 24 Mb/s; 48 Mb/s Mode:Master Extra:tsf=0000000000000000 Extra: Last beacon: 27270ms ago IE: Unknown: 0008786D753230315F31 IE: Unknown: 010882848B961224486C IE: Unknown: 030103 IE: Unknown: 32040C183060 IE: Unknown: 0706434E20010D14 IE: Unknown: 33082001020304050607 IE: Unknown: 33082105060708090A0B IE: Unknown: 050400010000 IE: WPA Version 1 Group Cipher : CCMP Pairwise Ciphers (1) : CCMP Authentication Suites (1) : PSK IE: IEEE 802.11i/WPA2 Version 1 Group Cipher : CCMP Pairwise Ciphers (1) : CCMP Authentication Suites (1) : PSK IE: Unknown: 2A0106 IE: Unknown: 2D1AAC0117FFFF000000000000000000000000000000000000000000 IE: Unknown: 3D1603000400000000000000000000000000000000000000 IE: Unknown: DD180050F2020101000003A4000027A4000042435E0062322F00 IE: Unknown: 0B0502000B127A IE: Unknown: DD07000C4300000000 IE: Unknown: DD06D4EE07010100

进行测试

sudo iwconfig wlan0 channel 3

123456iwconfigwlan0 IEEE 802.11bgn ESSID:"CH1" Mode:Managed Frequency:2.422 GHz Access Point: Not-Associated Tx-Power=31 dBm Retry short limit:7 RTS thr:off Fragment thr:off Power Management:on

重新进行信道扫描

信道没有发生变化。

结论

树莓派的 sudo iwconfig wlan0 channel 3极有可能是伪修改：即树莓派修改了某个寄存器的数值，但是并没有实际修改信道，这个可以通过进一步的研究进行验证。

树莓派开启热点功能

研究了一下树莓派的开启热点方法，都有点不科学，最后找到一个比较稳定且合适的方法，需要使用HDMI线和鼠标键盘(因为断掉wifi后树莓派会和电脑断连接、若有插网线则可以无视)具体操作如下：

创建WiFi热点使用的GitHub上一个开源项目：https://github.com/oblique/create_ap

下载开源项目包123sudo git clone https://github.com/oblique/create_apcd create_apsudo make install

可能会存在说树莓派连接不上github的可能性(ps:我就遇到了)

参考以下步骤：用电脑从github下载zip格式文件通过xftp将zip文件转存入树莓派 unzip xxx.zip文件12cd create_apsudo make install 运用该开源项目参考 No passphrase (open network):create_ap wlan0 eth0 MyAccessPoint WPA + WPA2 passphrase:create_ap wlan0 eth0 MyAccessPoint MyPassPhrase AP without Internet sharing:create_ap -n wlan0 MyAccessPoint MyPassPhrase Bridged Internet sharing:create_ap -m bridge wlan0 eth0 MyAccessPoint MyPassPhrase Bridged Internet sharing (pre-configured bridge interface):create_ap -m bridge wlan0 br0 MyAccessPoint MyPassPhrase Internet sharing from the same WiFi interface:create_ap wlan0 wlan0 MyAccessPoint MyPassPhrase Choose a different WiFi adapter drivercreate_ap --driver rtl871xdrv wlan0 eth0 MyAccessPoint MyPassPhrase No passphrase (open network) using pipe:echo -e "MyAccessPoint" | create_ap wlan0 eth0 WPA + WPA2 passphrase using pipe:echo -e "MyAccessPoint\nMyPassPhrase" | create_ap wlan0 eth0 Enable IEEE 802.11ncreate_ap --ieee80211n --ht_capab '[HT40+]' wlan0 eth0 MyAccessPoint MyPassPhrase Client Isolation:create_ap --isolate-clients wlan0 eth0 MyAccessPoint MyPassPhrase Systemd service

Using the persistent systemd service

Start service immediately:systemctl start create_ap Start on boot:systemctl enable create_ap License

FreeBSD

个人热点尝试的操作根据原开源项目内容设置自己需要的wifi 创建一个没有输入网络的热点

sudo create_ap -n wlan0 pi_wifi MyPassWord

遇到错误

ERROR: Your adapter can not be a station (i.e. be connected) and an AP at the same time

分析：应该是目前网络正在连接wifi，需要断开，turn off wifi ，重新进行尝试。

重新sudo create_ap -n wlan0 pi_wifi MyPassWord

报错：RTNETLINK answers: Operation not possible due to RF-kill

分析:应该是因为wifi被我之间断开，不能之间关闭只需要断开连接就行了

test：

这时用rfkill list查看所有无线设备

1230: phy0: Wireless LAN Soft blocked: yes Hard blocked: no

发现wlan0软件关闭了。

运行命令rfkill unblock wlan再查看无线设备

1230: phy0: Wireless LAN Soft blocked: no Hard blocked: no

wlan0软件开启。

再运行上面的sudo create_ap -n wlan0 pi_wifi MyPassWord出现：

wlan0: AP-ENABLED

成功开启热点

设置wifi的信道但是不要忘记了我们的目的，查了很久都没有人修改过热点的信道！！！可能大家不需要该热点的信道，但是作为搞无线网络通信的，我们不能只追求这个，我们要改信道！思考

方法1：使用命令行修改通信信道 sudo iwconfig wlan0 channel 3

方法2：查看该开源项目的内部文件，找到设置信道的方法

方法3：更换其他方式设置热点的信道

实验命令行修改信道 sudo iwconfig wlan0 channel 3 12Error for wireless request "Set Frequency" (8B04) : SET failed on device wlan0 ; Operation not supported.

直接报错，无法修改信道。

iwconfig 1234567wlan0 IEEE 802.11bgn Mode:Master Tx-Power=20 dBm Retry short limit:7 RTS thr:off Fragment thr:off Power Management:offlo no wireless extensions.eth0 no wireless extensions.

这说明什么，命令行在ap状态下是无效的，没办法直接这样修改，该方案不可行。

查看该开源项目的内部文件

这个热点开源项目一共有以下文件12bash_completion create_ap.conf create_ap.service LICENSE README.mdcreate_ap create_ap.openrc howto Makefile于是一个一个的找（只花了几分钟而已哈哈）

项目源代码12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576usage() { echo "Usage: "$PROGNAME" [options] [] [ []]" echo echo "Options:" echo " -h, --help Show this help" echo " --version Print version number" echo " -c Channel number (default: 1)" echo " -w Use 1 for WPA, use 2 for WPA2, use 1+2 for both (default: 1+2)" echo " -n Disable Internet sharing (if you use this, don't pass" echo " the argument)" echo " -m Method for Internet sharing." echo " Use: 'nat' for NAT (default)" echo " 'bridge' for bridging" echo " 'none' for no Internet sharing (equivalent to -n)" echo " --psk Use 64 hex digits pre-shared-key instead of passphrase" echo " --hidden Make the Access Point hidden (do not broadcast the SSID)" echo " --mac-filter Enable MAC address filtering" echo " --mac-filter-accept Location of MAC address filter list (defaults to /etc/hostapd/hostapd.accept)" echo " --redirect-to-localhost If -n is set, redirect every web request to localhost (useful for public information networks)" echo " --hostapd-debug With level between 1 and 2, passes arguments -d or -dd to hostapd for debugging." echo " --isolate-clients Disable communication between clients" echo " --ieee80211n Enable IEEE 802.11n (HT)" echo " --ieee80211ac Enable IEEE 802.11ac (VHT)" echo " --ht_capab HT capabilities (default: [HT40+])" echo " --vht_capab VHT capabilities" echo " --country Set two-letter country code for regularity (example: US)" echo " --freq-band Set frequency band. Valid inputs: 2.4, 5 (default: 2.4)" echo " --driver Choose your WiFi adapter driver (default: nl80211)" echo " --no-virt Do not create virtual interface" echo " --no-haveged Do not run 'haveged' automatically when needed" echo " --fix-unmanaged If NetworkManager shows your interface as unmanaged after you" echo " close create_ap, then use this option to switch your interface" echo " back to managed" echo " --mac Set MAC address" echo " --dhcp-dns Set DNS returned by DHCP" echo " --daemon Run create_ap in the background" echo " --pidfile Save daemon PID to file" echo " --logfile Save daemon messages to file" echo " --stop Send stop command to an already running create_ap. For an " echo " you can put the PID of create_ap or the WiFi interface. You can" echo " get them with --list-running" echo " --list-running Show the create_ap processes that are already running" echo " --list-clients List the clients connected to create_ap instance associated with ." echo " For an you can put the PID of create_ap or the WiFi interface." echo " If virtual WiFi interface was created, then use that one." echo " You can get them with --list-running" echo " --mkconfig Store configs in conf_file" echo " --config Load configs from conf_file" echo echo "Non-Bridging Options:" echo " --no-dns Disable dnsmasq DNS server" echo " --no-dnsmasq Disable dnsmasq server completely" echo " -g IPv4 Gateway for the Access Point (default: 192.168.12.1)" echo " -d DNS server will take into account /etc/hosts" echo " -e DNS server will take into account additional hosts file" echo echo "Useful informations:" echo " * If you're not using the --no-virt option, then you can create an AP with the same" echo " interface you are getting your Internet connection." echo " * You can pass your SSID and password through pipe or through arguments (see examples)." echo " * On bridge method if the is not a bridge interface, then" echo " a bridge interface is created automatically." echo echo "Examples:" echo " "$PROGNAME" wlan0 eth0 MyAccessPoint MyPassPhrase" echo " echo -e 'MyAccessPoint\nMyPassPhrase' | "$PROGNAME" wlan0 eth0" echo " "$PROGNAME" wlan0 eth0 MyAccessPoint" echo " echo 'MyAccessPoint' | "$PROGNAME" wlan0 eth0" echo " "$PROGNAME" wlan0 wlan0 MyAccessPoint MyPassPhrase" echo " "$PROGNAME" -n wlan0 MyAccessPoint MyPassPhrase" echo " "$PROGNAME" -m bridge wlan0 eth0 MyAccessPoint MyPassPhrase" echo " "$PROGNAME" -m bridge wlan0 br0 MyAccessPoint MyPassPhrase" echo " "$PROGNAME" --driver rtl871xdrv wlan0 eth0 MyAccessPoint MyPassPhrase" echo " "$PROGNAME" --daemon wlan0 eth0 MyAccessPoint MyPassPhrase" echo " "$PROGNAME" --stop wlan0"}

这一行明显及其关键，一看就是可以利用的代码。

其中：

echo " -c Channel number (default: 1)"

应该可以通过sudo create_ap -n wlan0 pi_wifi MyPassWord -c 2修改信道数值。

1234567WARN: brmfmac driver doesn't work properly with virtual interfaces and it can cause kernel panic. For this reason we disallow virtual interfaces for your adapter. For more info: https://github.com/oblique/create_ap/issues/203WARN: Your adapter does not fully support AP virtual interface, enabling --no-virtConfig dir: /tmp/create_ap.wlan0.conf.d6khWCULPID: 4794

wlan0应该是被占用了

修改信道

sudo create_ap --s wlan0

通过sudo create_ap -n wlan0 pi_wifi MyPassWord -c 1修改信道数值。

通过其他设备进行测试’iwlist scan’

扫描信道结果：1234567891011121314151617181920212223242526wlan0 Scan completed : Cell 01 - Address: 18:64:72:92:EC:81 Channel:1 Frequency:2.412 GHz (Channel 1) Quality=46/70 Signal level=-64 dBm Encryption key:on ESSID:"pi_wifi" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 6 Mb/s; 9 Mb/s 11 Mb/s; 12 Mb/s; 18 Mb/s Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s Mode:Master Extra:tsf=0000000000000000 Extra: Last beacon: 200ms ago IE: Unknown: 0007656475726F616D IE: Unknown: 010882840B0C12161824 IE: Unknown: 030101 IE: Unknown: 2A0102 IE: Unknown: 32043048606C IE: IEEE 802.11i/WPA2 Version 1 Group Cipher : CCMP Pairwise Ciphers (1) : CCMP Authentication Suites (1) : 802.1x IE: Unknown: 2D1AED111BFFFFFF0000000000000000000000000000000 000000000 IE: Unknown: 3D1601000A0000000000000000000000000000000000000 0 IE: Unknown: 7F080000080000000000 IE: Unknown: DD180050F2020101800003A4000027A4000042435E00623 22F00通过sudo create_ap -n wlan0 pi_wifi MyPassWord -c 11修改信道数值。通过其他设备进行测试’iwlist scan’

扫描信道结果：12345678910111213141516171819202122Cell 12 - Address: 18:64:72:92:EC:81 Channel:11 Frequency:2.462 GHz (Channel 11) Quality=66/70 Signal level=-44 dBm Encryption key:off ESSID:"pi_wifi" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s 9 Mb/s; 12 Mb/s; 18 Mb/s Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s Mode:Master Extra:tsf=0000000000000000 Extra: Last beacon: 17620ms ago IE: Unknown: 0003434832 IE: Unknown: 010882848B960C121824 IE: Unknown: 03010B IE: Unknown: 2A0100 IE: Unknown: 32043048606C IE: Unknown: 2D1A2C0003FF00000000000000000000000000000000000000000000 IE: Unknown: 3D160B001100000000000000000000000000000000000000 IE: Unknown: DD180050F2020101000003A4000027A4000042435E0062322F00 IE: Unknown: DD05000AEB0100 IE: Unknown: DD8E0050F204104A0001101044000102103B0001031047001000000000000010000000FCD7330F3A461021000754502D4C494E4B10230009544C2D57523734324E10240003372E3010420007312E312E312E331054000800060050F204000110110018576972656C657373204E20526F757465722057523734324E100800022288103C0001011049000600372A000120

成功修改信道！

总结

综上所示：

可以通过命令行修改功率

sudo iwconfig wlan1 txpower X

通过开源项目切换信道123sudo create_ap --s wlan0sudo create_ap -n wlan0 pi_wifi MyPassWord -c 11 1234567生成sshssh-keygen -t rsa -C "[email protected]"ssh-agent -sssh-add ~/.ssh/id_rsa 扩展：功率修改测试及方案开启热点 123sudo create_ap --s wlan0sudo create_ap -n wlan0 pi_wifi MyPassWord -c 11 修改功率

sudo iwconfig wlan1 txpower 30

检测功率

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